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Chronicling America vs Open Library

Same instrument, two spec sheets — measured, not claimed.

APIChronicling AmericaNEW—Open LibraryHEALTHY—
Uptime · 30d
Uptime · 90d—%—%
Uptime · 30d—%—%
P50 · ms——
P95 · ms——
Authnonenone
CORSnoyes
HTTPSyesyes
Card requirednono
Commercial useyesunclear
Data licensePublic domain / no known copyright (Library of Congress)Mixed — mostly open
Free tierFree — public-domain collection dataUnlimited within courtesy limits
Rate limitLoC throttles heavy crawling (see LoC API policy)Soft — identified UA appreciated
In directory since2026-07-052026-05-02
operationalpartialdownno data

Chronicling America vs Open Library: common questions

Which is more reliable, Chronicling America or Open Library?

On our scheduled checks, Open Library leads on measured uptime — Chronicling America at —% versus Open Library at —% over 90 days. These are our own probe results, not provider claims; the uptime bars above show the day-by-day record for both.

Do Chronicling America and Open Library need an API key?

Neither needs a paid key — Chronicling America is callable with no signup, and Open Library is callable with no signup. Both are quick to prototype with; rate limits still apply.

Can I call Chronicling America and Open Library from the browser?

Only Open Library is browser-friendly — it returns CORS headers over HTTPS. Chronicling America needs a server-side call or proxy, so factor that into which one fits a front-end project.

Are Chronicling America and Open Library free for commercial use?

Chronicling America allows commercial use on its free tier, and Open Library has unclear commercial terms. We track service terms and the data license as separate fields — see the Commercial use and Data license rows above, and confirm both before shipping either in a paid product.